Kabbalah zu Mischlej 1:7

Rabbi Aba said, "Serve Hashem in fear" 1. What fear is meant here? As we have established, it is written, "The fear of Hashem is the beginning of knowledge" (Mishlei 1:7) and "the fear of Hashem is the beginning of wisdom" (Tehilim 111:10), so the Holy One, blessed be He, is referred to in this name, "Fear of Hashem," Rabbi Elazar said: "Serve Hashem in fear," he who wishes to perform the service of his Master, from what point should he begin and to which area should he aim his service in order to unify the name of his Master? He repeats his words "with fear," because fear (which corresponds to Malchut) is the start (of service) going from below upwards.

בְּרִאשִׁית בָּרָא אֱלֹהִים. "In the beginning. Elohim created" (Gen. 1:1). This is the first and foremost precept of all. And this precept is called "the fear of the Hashem," which is called the "beginning." As it is written, "The Fear of Hashem is the beginning of wisdom" (Ps. 111:10); "The fear of Hashem is the beginning of knowledge" (Prov. 1:7). Because this fear (or awe) is called a beginning. And it is the gateway through which one enters into Faith. So based on this precept, the whole world is able to exist.